Lead Induced Oxidative DNA Damage among the Occupationally Exposed Workers: A Case-Control Study

Abstract

Introduction: The element Lead (Pb), which is considered as one of the most widely distributed enviornmental contaminants plays an important role in various industrial enterprises in India; hence bio-monitoring of occupationally exposed subjects becomes imperative. Adverse effects associated with Pb exposure, if identified at initial stages, can not only reduce the prolonged exposure but the carcinogenic risk as well. Aim: To evaluate the blood Pb levels and the associated DNA damage among the workers in Jaipur, Rajasthan, India who were occupationally exposed to Pb. Materials and Methods: This cross-sectional, case-control study was conducted for a period of three years from January 2016 to December 2018. A total of 220 subjects were included in the study (110 in each, Pb-exposed group and control group). Confounding factors like age, alcohol consumption, smoking and duration of working years were also investigated. The selection of cases was based on a predesigned questionnaire. The blood Pb levels were quantified by using an Inductively Coupled Plasma Mass Spectrometry (ICP-MS) technique based on triple quadropole technology (iCAP™ TQ ICP-MS) and the DNA damage in the blood lymphocytes was analysed using alkaline comet assay. The data were analysed through student’s t-test. Results: The mean blood Pb levels (38.03 µg/dL) and the mean % of tail DNA (14.80 µm) of the exposed group were found to be significantly higher when compared to the control group (4.89 µg/dL and 6.12 µm, respectively). The blood Pb values and the level of DNA damage were significantly different for smokers in comparison to non-smokers in the exposed group. The blood Pb levels of the exposed subjects positively correlated with the years of exposure. Higher DNA damage was also found in subjects with prolonged exposure to Pb. Conclusion: Present study results showed that exposure to Pb induces genotoxic effects in peripheral lymphocytes, as measured by comet assay, a rapid and sensitive method suitable for bio-monitoring studies. The increased blood levels and the associated DNA damage observed in the exposed subjects mandates the routine periodical screening of such workers for evaluation of the genotoxic effects of Pb. Effective and efficient preventive measures need to be taken, not only to improve the working conditions but also to ensure better safety measures to minimise the occupational exposure of the workers towards Pb.

Keywords

• blood lead level
• comet assay
• genotoxicity
• occupational lead exposure